silk/resampler_private_down_FIR.c

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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "SigProc_FIX.h"
#include "resampler_private.h"

static inline opus_int16 *silk_resampler_private_down_FIR_INTERPOL0(
    opus_int16 *out, opus_int32 *buf2, const opus_int16 *FIR_Coefs, opus_int32 max_index_Q16, opus_int32 index_increment_Q16){

    opus_int32 index_Q16, res_Q6;
    opus_int32 *buf_ptr;
    for( index_Q16 = 0; index_Q16 < max_index_Q16; index_Q16 += index_increment_Q16 ) {
        /* Integer part gives pointer to buffered input */
        buf_ptr = buf2 + silk_RSHIFT( index_Q16, 16 );

        /* Inner product */
        res_Q6 = silk_SMULWB(         silk_ADD32( buf_ptr[ 0 ], buf_ptr[ 15 ] ), FIR_Coefs[ 0 ] );
        res_Q6 = silk_SMLAWB( res_Q6, silk_ADD32( buf_ptr[ 1 ], buf_ptr[ 14 ] ), FIR_Coefs[ 1 ] );
        res_Q6 = silk_SMLAWB( res_Q6, silk_ADD32( buf_ptr[ 2 ], buf_ptr[ 13 ] ), FIR_Coefs[ 2 ] );
        res_Q6 = silk_SMLAWB( res_Q6, silk_ADD32( buf_ptr[ 3 ], buf_ptr[ 12 ] ), FIR_Coefs[ 3 ] );
        res_Q6 = silk_SMLAWB( res_Q6, silk_ADD32( buf_ptr[ 4 ], buf_ptr[ 11 ] ), FIR_Coefs[ 4 ] );
        res_Q6 = silk_SMLAWB( res_Q6, silk_ADD32( buf_ptr[ 5 ], buf_ptr[ 10 ] ), FIR_Coefs[ 5 ] );
        res_Q6 = silk_SMLAWB( res_Q6, silk_ADD32( buf_ptr[ 6 ], buf_ptr[  9 ] ), FIR_Coefs[ 6 ] );
        res_Q6 = silk_SMLAWB( res_Q6, silk_ADD32( buf_ptr[ 7 ], buf_ptr[  8 ] ), FIR_Coefs[ 7 ] );

                /* Scale down, saturate and store in output array */
        *out++ = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( res_Q6, 6 ) );
    }
    return out;
}

static inline opus_int16 *silk_resampler_private_down_FIR_INTERPOL1(
    opus_int16 *out, opus_int32 *buf2, const opus_int16 *FIR_Coefs, opus_int32 max_index_Q16, opus_int32 index_increment_Q16, opus_int32 FIR_Fracs){

    opus_int32 index_Q16, res_Q6;
    opus_int32 *buf_ptr;
    opus_int32 interpol_ind;
    const opus_int16 *interpol_ptr;
    for( index_Q16 = 0; index_Q16 < max_index_Q16; index_Q16 += index_increment_Q16 ) {
        /* Integer part gives pointer to buffered input */
        buf_ptr = buf2 + silk_RSHIFT( index_Q16, 16 );

        /* Fractional part gives interpolation coefficients */
        interpol_ind = silk_SMULWB( index_Q16 & 0xFFFF, FIR_Fracs );

        /* Inner product */
        interpol_ptr = &FIR_Coefs[ RESAMPLER_DOWN_ORDER_FIR / 2 * interpol_ind ];
        res_Q6 = silk_SMULWB(         buf_ptr[ 0 ], interpol_ptr[ 0 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 1 ], interpol_ptr[ 1 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 2 ], interpol_ptr[ 2 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 3 ], interpol_ptr[ 3 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 4 ], interpol_ptr[ 4 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 5 ], interpol_ptr[ 5 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 6 ], interpol_ptr[ 6 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 7 ], interpol_ptr[ 7 ] );
        interpol_ptr = &FIR_Coefs[ RESAMPLER_DOWN_ORDER_FIR / 2 * ( FIR_Fracs - 1 - interpol_ind ) ];
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 15 ], interpol_ptr[ 0 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 14 ], interpol_ptr[ 1 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 13 ], interpol_ptr[ 2 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 12 ], interpol_ptr[ 3 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 11 ], interpol_ptr[ 4 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 10 ], interpol_ptr[ 5 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[  9 ], interpol_ptr[ 6 ] );
        res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[  8 ], interpol_ptr[ 7 ] );

        /* Scale down, saturate and store in output array */
        *out++ = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( res_Q6, 6 ) );
    }
    return out;
}


/* Resample with a 2x downsampler (optional), a 2nd order AR filter followed by FIR interpolation */
void silk_resampler_private_down_FIR(
    void                            *SS,            /* I/O: Resampler state                         */
    opus_int16                        out[],            /* O:    Output signal                             */
    const opus_int16                    in[],            /* I:    Input signal                            */
    opus_int32                        inLen            /* I:    Number of input samples                    */
)
{
    silk_resampler_state_struct *S = (silk_resampler_state_struct *)SS;
    opus_int32 nSamplesIn;
    opus_int32 max_index_Q16, index_increment_Q16;
    opus_int16 buf1[ RESAMPLER_MAX_BATCH_SIZE_IN / 2 ];
    opus_int32 buf2[ RESAMPLER_MAX_BATCH_SIZE_IN + RESAMPLER_DOWN_ORDER_FIR ];
    const opus_int16 *FIR_Coefs;

    /* Copy buffered samples to start of buffer */
    silk_memcpy( buf2, S->sFIR, RESAMPLER_DOWN_ORDER_FIR * sizeof( opus_int32 ) );

    FIR_Coefs = &S->Coefs[ 2 ];

    /* Iterate over blocks of frameSizeIn input samples */
    index_increment_Q16 = S->invRatio_Q16;
    while( 1 ) {
        nSamplesIn = silk_min( inLen, S->batchSize );

        if( S->input2x == 1 ) {
            /* Downsample 2x */
            silk_resampler_down2( S->sDown2, buf1, in, nSamplesIn );

            nSamplesIn = silk_RSHIFT32( nSamplesIn, 1 );

            /* Second-order AR filter (output in Q8) */
            silk_resampler_private_AR2( S->sIIR, &buf2[ RESAMPLER_DOWN_ORDER_FIR ], buf1, S->Coefs, nSamplesIn );
        } else {
            /* Second-order AR filter (output in Q8) */
            silk_resampler_private_AR2( S->sIIR, &buf2[ RESAMPLER_DOWN_ORDER_FIR ], in, S->Coefs, nSamplesIn );
        }

        max_index_Q16 = silk_LSHIFT32( nSamplesIn, 16 );

        /* Interpolate filtered signal */
        if( S->FIR_Fracs == 1 ) {
            out = silk_resampler_private_down_FIR_INTERPOL0(out, buf2, FIR_Coefs, max_index_Q16, index_increment_Q16);
        } else {
            out = silk_resampler_private_down_FIR_INTERPOL1(out, buf2, FIR_Coefs, max_index_Q16, index_increment_Q16, S->FIR_Fracs);
        }

        in += nSamplesIn << S->input2x;
        inLen -= nSamplesIn << S->input2x;

        if( inLen > S->input2x ) {
            /* More iterations to do; copy last part of filtered signal to beginning of buffer */
            silk_memcpy( buf2, &buf2[ nSamplesIn ], RESAMPLER_DOWN_ORDER_FIR * sizeof( opus_int32 ) );
        } else {
            break;
        }
    }

    /* Copy last part of filtered signal to the state for the next call */
    silk_memcpy( S->sFIR, &buf2[ nSamplesIn ], RESAMPLER_DOWN_ORDER_FIR * sizeof( opus_int32 ) );
}